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Time-Resolved Research (XSD-TRR)

The TRR group has full and partial operational responsibility for 7 experimental stations at 5 beamlines. There are 6 undulator end stations (7-ID-B, 7-ID-C, 7-ID–D, 8-ID-E, 8-ID-I and 14-ID-B) and one bending magnet end station (7-BM-B). Time-resolved pump-probe techniques using, most often, high-power lasers as the pump, are performed in stations 7-ID-C and 7-ID-D and 14-ID-B [which the X-ray Science Division (XSD) runs in partnership with BioCARS]. 7-ID-B is white-beam capable and hosts experiments that probe ultrafast fluid dynamics in high-pressure, high velocity sprays. Station 7-BM-B complements the work performed in 7-ID-B by performing spatial mapping of high pressure, high velocity sprays and aerosols via time-resolved radiography and fluorescence measurements. 8-ID-E primarily supports grazing-incidence scattering (GIXS) devoted to measuring the morphology of organic thin films. 8-ID-I, and to a lesser extent 8-ID-E, apply x-ray photon correlation spectroscopy (XPCS) to study the stability of and very low energy excitations in soft (8-ID-I) and hard (8-ID-E) materials. In addition to the x-ray-beamlines, our group maintains and enhances high-power ultrafast laser systems at 7-ID and 14-ID.

7-BM-B is used for time-resolved mapping measurements of the spatial distribution and dynamics of high density and high-speed sprays and aerosols. Radiographic, tomographic and fluorescence techniques are employed with μm spatial resolution and time resolution as fine as the x-ray pulse separation. Measurements performed at 7-BM-B have numerous technological applications including those related to energy sources for propulsion and transportation systems. Consequently, much of the work is performed in partnership with industry (USCAR partners and suppliers) and defense. The construction of 7-BM-B was partially funded by DOE-EERE.

7-ID-B is a white-beam-capable station primarily used for ultra-fast imaging of high density and high-speed sprays. Unique imaging capabilities include the ability to image the internal motion of operating fuel injectors and to perform single-x-ray-shot imaging of dense sprays. As in 7-BM-B, much of the work in this station is performed in collaboration with industrial users like USCAR partners and their suppliers.

7-ID-C has dedicated diffraction and nanoprobe diffraction set-ups that provide Å resolution (reciprocal space) ultrafast time-resolved measurements of pumped materials. Pumps include an ultrafast high-power laser beam with 1 kHz rep-rate, an available high-rep-rate (54 kHz - 6.5 MHz) high-power laser and terahertz (THz) radiation. Typical x-ray-beam sizes are 50 μm for samples mounted on a large 6-circle Huber diffractometer while a new zone-plate set-up provides 300 nm resolution for samples mounted on a compact Huber diffractometer. A variety of sample environments are available. An RF-deflection streak camera is also available for measurements requiring time resolution within the x-ray pulse length (≈100 ps). Work in this station is relevant to a fundamental understanding of excitations and phase diagrams of emerging complex materials.

7-ID-D is primarily devoted to pump-probe studies of ultrafast transient states of photoactive molecules in solution via the time-resolved incarnations of x-ray techniques such as XANES, EXAFS, x-ray emission (XES) spectroscopy and x-ray diffuse scattering (XDS). An ultrafast high-rep-rate (54 kHz - 6.5 MHz), high-power laser is typically used as the pump. Novel x-ray emission spectrometers are being developed and deployed that, combined with the high-rep-rate laser beams, allow the excited states of small and dilute quantities of designer photoactive molecules to be probed with high fidelity. Work performed in 7-ID-D is relevant to the fundamental understanding of photochemistry with ultimate application to artificial photosynthesis. Much of the work in this station is performed in collaboration with the XSD-AMO group.

8-ID-E is primarily devoted to grazing incidence x-ray scattering (GIXS) measurements of the structure and processing kinetics of organic thin films. Measurements are made in both the wide-angle geometry (GIWAXS) (sensitive to molecular packing) and small-angle geometry (GISAXS) (sensitive to mesoscale ordering). A high-speed version of the Pilatus 1M detector provides wide-angle time-resolved (> 10 ms) data collection. A variety of sample environments are available for in situ measurements of films. Recent research at 8-ID-E is focused on correlating the structure of OPV thin films with light-harvesting performance and probing defects in self-assembled block copolymers with applications to nanolithography. 8-ID-E also hosts a large angle x-ray photon correlation spectroscopy program (XPCS) that examines very low energy fluctuations in hard condensed matter.

8-ID-I hosts the small angle XPCS program that examines very low energy fluctuations in hierarchically ordered soft materials such as polymer nanocomposites and glassy colloidal suspensions. Temperature and sample composition are traditional independent variables but considerable flexibility is provided for user-supplied sample environments such as rheometers, strain cells and deposition chambers. High-gain, high-resolution increasingly fast area detectors are used for measuring the time series of speckle patterns. An efficient and user-friendly interface to APS high-performance computing (HPC) resources provides rapid data reduction. Work in this station is relevant to understanding the stability of novel forms of matter with ultimate application to the food and consumer products industries. 8-ID-I hosts the small angle XPCS program that examines very low energy fluctuations in hierarchically ordered soft materials such as polymer nanocomposites and glassy colloidal suspensions. Temperature and sample composition are traditional independent variables but considerable flexibility is provided for user-supplied sample environments such as rheometers, strain cells and deposition chambers. High-gain, high-resolution increasingly fast area detectors are used for measuring the time series of speckle patterns. An efficient and user-friendly interface to APS high-performance computing (HPC) resources provides rapid data reduction. Work in this station is relevant to understanding the stability of novel forms of matter with ultimate application to the food and consumer products industries.

14-ID-B is operated as a partnership between BioCARS and XSD and is specialized in ultrafast time resolved techniques such as laser pump high-flux x-ray probe in both pink and monochromatic x-ray-beam modes of operation. Roughly 35% of the user time is earmarked for work in physics and chemistry. First harmonic coverage is from 7 to 19 keV. At the sample location, the x-ray beam is 90 × 20 μm2 (H × V) in either pink or monochromatic mode. A chopper/shutter system allows isolation of single or multiple X-ray pulses in both 24-bunch and hybrid modes with per pulse energies of 20 and 80 μJ, respectively. The laser system provides picosecond optical pulses from 350 to 2000 nm with energies exceeding 100 μJ/pulse. The accessible timescales range from 100 picoseconds to milliseconds or longer. Most experiments are Laue scattering though novel set ups are frequently supported that make use of the uniquely powerful x-ray source. A large area, 10 Hz integrating X-ray CCD is newly installed. Work performed in 14-ID-B is relevant to the fundamental understanding of light-capture in a variety of systems.

Laser Systems

Specifications below provide general guidelines. Specific capabilities and requirements should be discussed with the beamline staff.

System

Station

Rep-rate

Pulse
Length

Wavelength

Energy per
Pulse

Ti:Sapph

7-ID-C, 7-ID-D

1 kHz

100 fs

800, 400 nm

200 μJ

Ti:Sapph with OPA

7-ID-C

1 kHz

100 fs

200nm - 20 μm

10 μJ

Duetto*

7-ID-D

54 kHz - 6.5 MHz

10 ps

1 or 0.5 μm

10 μJ

Spectra Ti:Sapph

14-ID-B

< 1 KHz

1 ps

350 nm - 2 μm

200 μJ

Comments:
*Portable system primarily operated and maintained by XSD-AMO in Station 7-ID-D. Available for use in other stations via collaboration or permission of XSD-AMO group and with appropriate safety considerations.